The present invention relates to a device for use when maintenance work is being performed on an existing oil or gas well having two or more strings or pipe running therefrom. In particular, the present invention is related to a device for distributing the force exerted downward by maintenance equipment on a wellhead over the horizontal surface of the wellhead rather than concentrating the force on a single threaded connection.
It is common practice in the oil and gas industry to install what is known as a "Christmas Tree" on a completed gas or oil well. Some Christmas trees have provisions for receiving two or more strings of pipe contained in one well, each string producing oil or gas from a separate zone. Such Christmas trees are well known in the art and are in wide spread use in the oil industry. For example, U.S. Pat. No. 2,889,886 contains a description of a Christmas Tree in column 1 thereof. Various other wellhead apparatuses are disclosed in U.S. Pat. Nos. 3,028,917; 3,050,120 and 3,059,698.
Occassionally it is necessary to perform maintenance operations on completed wells having a Christmas tree connected thereto. Such maintenance work includes sand washing with fluid, nitrogen or foam, fishing for lost wireline tools, washing perforations and acidizing, running and pulling production strings, resetting weight on packers, and the like.
To perform such maintenance work, a large amount of heavy equipment must be attached to the top of the Christmas tree over the individual string of pipe which is being maintained. The equipment above the Christmas tree is generally referred to as a hydraulic workover unit or workover apparatus and may actually perform the maintenance work on the individual string of pipe while the pipe is under pressure from the fluids in the pipe. Such hydraulic workover equipment is very heavy and extends a considerable distance above the top of the Christmas tree to which it is connected. This distance may range from ten (10) to thirty (30) feet or more above the top of the Christmas tree. To hold this equipment in position, commonly cables or guy wires are extended from the equipment to the ground.
Almost the entire weight of the equipment above the Christmas tree is concentrated on a single threaded connection in the Christmas tree into which the bottom of the hydraulic workover unit is threaded. Forces as great as 60,000-80,000 pounds may be applied to the single threaded connection in the Christmas tree leading to the string of pipe on which maintenance operations are being performed.
Thus, it can be seen that such heavy equipment extending far into the air above the Christmas tree and the weight concentrated on a single threaded connection, which may vary from 23/8 to 27/8 inches in diameter, presents a very dangerous condition for the workmen in the area and for the equipment being utilized. If the hydraulic workover equipment is not balanced carefully on the Christmas tree, the bottom portion of the workover equipment which is threaded in the Christmas tree can easily be broken due to the great amount of weight being concentrated on a small threaded connection. In the past many serious accidents have occurred due to the cracking or breaking of the pipe extended from the hydraulic workover unit and threaded into the Christmas tree. Such a cracking or breaking can result in the collapse of the entire hydraulic workover rig and injury to personnel in the vicinity.
Accordingly, it is an object of the invention to provide a means for distributing the weight of a hydraulic workover unit connected to a Christmas tree over the horizontal surface of the Christmas tree rather than entirely on the threaded connection into which the bottom portion of the hydraulic workover rig is connected.